Spectro-Chemical Analysis of the Speciation of Cadmium on Montmorillonite in the Presence of Soil Microbial Biomass

Here we report on a spectro-chemical approach to investigate the adsorption of dissolved Cd ions to montmorillonite (M) in the presence of a mixed consortium of soil bacteria. Results indicate that the order of metal-loading was M- microbial complex > microbial biomass > M. Surface interactions of Cd with M-microbial complex have also been confirmed, and we speculate that after binding to M, additional proton binding sites on microbial cells function as binding sites for Cd ions thereby enhancing the metal binding capacity of the mineral. There is also evidence to suggest that hydrogen bonding, cation bridging and ion-exchange are important mechanisms in the adsorption of metal ions to clay-organo complexes.